Conventional progressive addition lenses are one-piece lenses having an upper viewing zone (‘the distance zone’), a lower viewing zone (‘the near zone’), and a progressive corridor (‘the intermediate zone’) extending between the distance zone and the near zone. The corridor provides a gradual power progression from the distance zone to the near zone without any dividing line or prismatic jump.
Although early progressive addition lenses were somewhat crude in design, they have consistently improved in performance over the past few decades. The improvement in performance has been a causative factor in significantly increasing patient demand for these categories of lenses to the point where lens dispensers and manufacturers today offer a large number of different progressive lens designs. There is thus available to a dispenser a large number of lens designs that may be dispensed to a wearer.
Typically, dispensing a progressive addition lens wearer involves a dispenser, such as an optometrist, selecting a particular progressive addition lens design from a range of semi-finished progressive lens designs.
A dispensing process that starts with the selection of a semi-finished lens, typically involves a dispenser selecting a series of progressive addition lens designs having a base curve that corresponds to the wearer's requirements, and then selecting, from within that series, a progressive addition lens design having an addition power that is suitable for the wearer. The selected semi-finished lens is then finished, by adding a prescription surface, to provide a finished progressive ophthalmic lens that meets the wearer's prescription requirements.
Since different wearer's experience different levels of presbyopia, different series of semi-finished lenses are provided for different addition powers, typically from 0.75 D to 3.50 D in 0.25 D increments (that is, twelve different lens designs for each series). Furthermore, a single product intended as a general purpose solution for presbyopia needs to be able to correct vision for a wide range of prescriptions, typically between −10.00 D and +6.00 D or more. However, since a single base curve can ensure satisfactory optics only over a range of prescription powers much narrower than is required, lens manufacturers typically create a range of lens series or base curves to satisfy this requirement. Indeed, typically, there may between four and eight lens series in a progressive addition lens (PAL) product.
There may thus be a large number of progressive addition lens designs that are able to be dispensed by a dispenser. Such a large number of designs complicates the dispensing process. The situation is exacerbated further as a result of different lens manufacturers providing different lens products and series. As a result, in dispensing a particular design for a wearer a dispenser must select a particular design from a range of different designs.
Alternatively, recent progressive addition lens designs provide a ‘freeform’ product where the progressive addition lens design is uniquely generated in response to customer needs. Here the selection of a particular design will often be out of the control of the optometrist or dispenser.
It is an aim of the present invention to provide a system and/or method that assists the dispenser in dispensing and/or designing a progressive lens design for a patient.